A well system (e.g., oil or gas wells for extracting fluids from a subterranean formation) can include sensors and gauges positioned downhole for sensing conditions within the wellbore (e.g., temperature, pressure, vibrations, etc.). A splice housing can receive an optical fiber (“fiber”) for connection to an optical sensor or gauge. The fiber can be fixed at either end of a splice tray of the splice housing assembly. The length of the fiber within the splice housing can be approximately the same length as the splice tray. The splice housing, including the splice tray, and the fiber can increase in temperature when downhole. The splice housing and splice tray can expand in length much greater than the fiber, for example due to differences in the thermal expansion of metal and glass. This can create stress in the fiber, which can affect the optical properties of the signal, or in some cases can cause the fiber to break.
A splice housing can also have a secondary Y-splitter attached to the end of the splice housing to break out a fiber for connection to a sensor (e.g., a pressure sensor). The addition of the secondary Y-splitter can increase the length of the mandrel used to mount the splice housing. An increase in the length of the mandrel can increase costs associated with machining the mandrel.